Posted by Gordon England on May 23, 2003 at 16:03:39:
In Reply to: Minimum Coating thickness of Aluminium Metallising posted by Sandeep Jaikishen on May 23, 2003 at 11:24:43:
: We had specified Zn/Al metallization of minm 40 microns for our LPG cylinders prior to liquid painting. But I came to know that Aluminium metallisation should never be lesser than 75 microns. Can somebody please tell me, why it should be minimum 75 microns and refer me some standards, so as to amend our specification.
: Regards
: Sandeep
Hi Sandeep
Most national and international standards for zinc and aluminium thermal spray anti-corrosion coatings cover nominal coating thickness of 100 microns and upwards.
Generally, as these are sacrificial coatings the thicker the coating the longer they last.
In my experience of the LPG cylinder manufacturers, many aim at a similar coating thickness as yours (some in fact lower). One problem with very thin coatings is ensuring even coverage. It can be difficult to measure at this level as you are approaching the individual particle splat thickness. So it is possible to have next to no coating material on the surface, yet have thickness measurements indicating the minimum thickness has been achieved.
At the end of the day it is a balance between quality/part life and economics. Setting your minimum thickness to 75 microns will double your your spray material usage and take twice as long to coat! but your customer may see his cylinders lasting very much longer.
Regards Gordon
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